


What's Yours Is Mine

by Evil_Knitter (Nichneven13)



Category: Supernatural
Genre: Dean and Cas make it better, Dean teaches Sam what to do, Established Dean/Cas relationship, First Time, M/M, Sam is lonely, Sam likes it, Threesome
Language: English
Status: Completed
Published: 2015-11-04
Updated: 2015-11-04
Packaged: 2018-04-29 20:10:19
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,839
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5140964
Author URL: https://archiveofourown.org/users/Nichneven13/pseuds/Evil_Knitter
Summary: <blockquote class="userstuff">
              <p>Sam feels left out. Cas has an idea to make him feel better.  (Really, it's threesome boy sex.)</p>
            </blockquote>





	What's Yours Is Mine

In the beginning, there was Mary and John. They added Dean out of love and then Sam out of accident. The time of Mary and John and Dean and Sam was briefly lived, and then it was John and Dean and Sam. Before too long, it morphed and changed, at times becoming Dean and Sam, then John and Dean, and finally, after John died, there was Dean and Sam for keeps. Except there was the day or so it was just Dean. And the four months it was just Sam.

And then there was the time it was Dean and Sam and Castiel. Those times were tense and sometimes awkward, but Sam could not understand why. Until the day he figured out that it was no longer Dean and Sam and Castiel.

The night Sam knew, was the night he rounded the corner of the seedy motel the Winchesters would call home for the night—on his way to get ice—and found his brother on his knees. Castiel’s eyes had landed on Sam, but instead of pushing his brother away, the angel had thrust his hips forward, forcing Dean to take more. Sam had turned and fled, wanting to forget, but understanding at last that that it was Dean and Castiel.

Sam watched Castiel orbit his brother, no matter if they were in the heat of battle or the heat of morning coffee and donuts. And he watched Dean’s eyes track the angel’s movement and position as if he was a moth and Castiel was a flame. The little, unconscious touches followed soon after that. A hand on a sleeve, a knee against a knee, a finger on a wrist, a forehead against a shoulder. They were fleeting touches, but they carried a world’s worth of import.

Castiel— _Cas_ —integrated into their nomadic life without discussion, just as he’d slipped into Dean’s bed the first time without discussion. The time for Dean and Sam to talk and decide together was gone. Sam didn’t ask and Dean didn’t tell. It was Castiel who got to talk to Dean.

Sam found himself jealous and yearning. But not for Dean. He knew, logically, that Dean was always his. His brother, his protector, his savior.

What Sam yearned for was Cas’ silent adoration. With Dean and Cas’ kisses on display to Sam, he yearned for Cas’ worshipful mouth on his own. He didn’t begrudge his older brother’s happiness; he just wanted to share in it, like they had shared everything their entire lives. They’d shared women in the past, so Cas should be no different.

Except, of course, that Cas was very different.

**

 

“Your brother is hurting,” Cas said during a rare break from Sam, who had gone to a bar seeking his own brand of peace.

“I don’t know how to help him,” Dean said, acknowledging that yes, there was something wrong with his brother. “He doesn’t talk to me anymore.”

“He wants a piece of our happiness,” Cas told him, stroking lazy fingers over the exposed skin of Dean’s arm. He enjoyed touching Dean’s skin, which Dean knew and made a point of shedding his layers whenever the moment presented itself. “Sam used to be everything to you. He feels lost now.”

“A piece of our happiness?” Dean furrowed his brow and considered the meaning behind the angel’s riddled words. He was something of an expert when it came to translating Cas. “Do you mean he wants to fuck you?”

“Yes,” Cas nodded.

“No way,” was the immediate response.

“You know I do not love Sam,” Cas said. Dean growled but nodded because he knew that without hesitation. “If he can take comfort in this body, how can we not allow it?”

“Because you are mine,” Dean said, tightening his hold around Cas’ waist.

“Would you feel the same if I was inside a different vessel?” Cas asked, pressing a soft kiss to Dean’s collarbone. “If I was in an old woman’s body? Would I still be yours?”

“That’s not fair, Cas,” Dean huffed. This conversation was too close to discussing their feelings, which they avoided at all costs. They  _knew_  what they had, what they were to each other; there was no need for superfluous words. “You know the answer to that.”

“Then you understand that what we share, what I give to you is not this body,” Cas said in a low voice, as if coaxing a kitten from under the couch. “I give you myself, my soul. I will not give that to your brother.”

“I don’t want him to touch you,” Dean said, the most honest explanation he could give. His stomach churned at the thought of seeing his brother’s hands, mouth, dick on Cas. He was an open-minded kind of man, well not really, but he was willing to listen to reason. Cas had always been reason and logic to Dean.

“Dean…” Cas started with a wheedling bend to his voice.

“Cas, don’t ask me to do this.”

 “I  _am_  asking you to do this,” Cas said firmly. Dean would capitulate because he could deny Cas nothing, but he did not want to allow Sam to trespass on territory Dean had claimed so many times before. Cas lifted his hands to Dean’s face, pulling him down for a tender kiss. “Because you love Sam. You have always taken care of Sam; this time, let me help you.”

In exact karmic timing, the motel door opened and Sam slipped inside, bringing with him the smell of cigarette smoke and loneliness. He paused at the sight of a shirtless Dean and fully clothed Cas in the middle of the room.

“Sam.”

Sam cringed at the roughness of Dean’s voice. He prepared to duck back out of the room, to sleep in the Impala. He knew Dean and Cas often had sex when they presumed him to be asleep, but never when he was so obviously awake and aware.

“Don’t go,” Cas said, breaking away from Dean and slowly approaching his lover’s brother.

“ _Sam_ ,” Dean said again, not turning around. He didn’t know what he meant to say, but he hoped that his brother would somehow know.

“Dean and I would like you to join us tonight,” Cas said, simplicity in motion.

“Uh, sure,” Sam shrugged out of his jacket and tossed it over an empty chair, because an invitation into the inner sanctum of Dean and Cas was a rare and beautiful thing. “What are we doing?”

Cas didn’t respond with words. He worked his arms out of his overshirt, throwing it on top of Sam’s jacket. Keeping his eyes trained on Sam, he reached down and slid his belt out of his pants. Dean kept his back to the two men, but his shoulders tensed at the sound of leather pulling away from Cas’ jeans.

“Cas,” Sam gulped and searched the room for some distraction. “What are you doing? I’ll just go back to the bar—sleep in the Impala—”

“I want you to fuck me,” Cas said clearly, without apology. He pulled his shirt over his head and dropped it to the floor as he toed his shoes off. “I want Dean to show you how he fucks me.”

“Cas,” Dean bit out, clinging to his plea to end this torture.

“No, Cas,” Sam stepped back quickly, but ran into the door at his back. He knew he had to turn the knob and flee, but he was pinned in time and space. “You and Dean.”

“And you, Sam,” Cas said with a smile, but at Dean’s disgruntled sound, quickly amended. “At least for tonight.”

“Dean?” Sam asked, but he wasn’t sure what question he meant to ask.

“Dean,” Cas said, that one word the only bit of speech necessary to fence Dean in and lock him tight.

“Yeah, Sammy,” Dean finally turned and with great effort, looked his brother in the eye, answering the question Sam hadn’t asked aloud. “You can.”

Sam stood where he was planted, attempting to process the information being hurled at him. His brother was inviting him back in and despite his reservations, there was no way he would reject it. He relegated the cost of incest to the back of his mind; after all, the Winchester brothers had long since shrugged off the rules and laws of mortal men.

Cas took another measured step toward the younger Winchester, his eyes fixed and determined. His sure hands landed on Sam’s waist and drew him close. Sam swayed forward, captivated, ready to let Cas kiss away his hesitance.

“Cas,” Dean said, suddenly behind his lover, pulling him away from Sam. He couldn’t stand it; he would do anything to keep Sam from profaning Castiel’s lips. “Wait. Let me.”

Sam tensed, watching as the pair before him kissed baldly. His fingers twitched, but he remained frozen, waiting for instruction… for permission.

Dean reached for his brother, never losing contact with Cas’s mouth, and dragged him across the slim space between them. Finally, he turned his head, with Sam pressed indecently against his side, and kissed him hard. He poured his anger and frustration into the kiss, punishing his little brother for robbing him of his angel’s absolute attention.

Cas watched the brothers, and smiled. They were awkward together, not quite fitting as well as he’d imagined. He reached up, fascinated by the joining of two solid and good souls, and smoothed away the angry lines around Dean’s lips. “It’s okay,” he whispered as he slipped his index finger into Dean’s mouth, hooking behind his teeth. He used his middle finger to catch Sam the same way. “We’ll make it okay.”

The brothers moaned together, united at last. Dean pulled away first, stepping away from Sam to pull Castiel between them. He made sure his lover was facing him, but Sam seemed content to suckle and nip at Cas’s bare shoulders and neck.

Cas found Sam’s mouth and hands pleasing, but not in the same way as Dean’s. He did not doubt, not once, that he would ever confuse the touches or feelings of either brother. He let his head fall forward onto Dean’s shoulder as the trio shuffled as one to the nearest too-small bed.

In less time than rational, Cas was on his back between the two Winchesters, ready and eager to close the gap between the once symbiotic brothers. Sam had his hand wrapped firmly around Cas’s dick, pumping in a steady rhythm that had caught Dean’s intense stare.

“Dean,” Cas sighed, wanting those familiar hands on his body. He reached out and grazed the bottom of the handprint scar on Dean’s arm, making him jerk and groan. “Show him… Touch me.”

Without hesitation, Dean took Sam’s hand from Cas’ cock and sucked two of his brother’s fingers into his mouth, coating them with spit. Sam’s head dropped back as he moaned at the sensation. It was wrong, he knew it, but damn, it felt amazing.

“Don’t check out on me, Sammy,” Dean commanded as he pulled Sam’s fingers out of his mouth. His voice was low as if telling a secret, which he was, if teaching his little brother how to debauch an angel counted. “Pay attention.”

Sam would pay a million fucking dollars worth of attention when Dean sounded like that. He focused his eyes on his damp fingers; watching as Dean guided him down, between Cas’ spread legs. Each time Dean’s skin brushed over Cas, the angel made a delicious sound deep in his throat.

“Start with one,” Dean said, and helped Sam make a sweep over Cas’ puckered hole. “Slowly. He likes it when you go in with a wiggle.”

Sam drew in a shaky breath and cast a brief look up at Cas, whose head was thrown back against the pillows and whose hands were holding onto the headboard as if he was dangling twenty floors from the ground.

With Dean’s help, he pushed into Cas, wiggling his fingertip from side to side as he advanced. “Good, Sammy, that’s good,” Dean said, pushing his lover’s knee wider on the bed and crawling in the extra space. Sam watched as Dean dove down, and without warning, pressed the flat of his tongue to Cas’ hole, and by extension, Sam’s finger.

Cas cried out and bucked off the bed, pushing Sam’s finger up to his third knuckle. Dean seemed ready for the reaction, moving back carefully, but maintaining the intimate contact. Sam reached out blindly and grabbed his brother’s shoulder to steady himself. His eyes were glued to the sinful lapping of Dean’s tongue.

Gently, Dean wrapped his hand around Sam’s wrist and silently encouraged him to move the finger embedded in the writhing angel. Sam was quick to follow the recommendation, carefully pulling his finger back and then meticulously thrusting forward again. Cas’ hands flew up and landed unerringly on the heads of the Winchester boys, his fingers curling around Sam’s long hair and cupping the back of Dean’s.

Sam rocked forward to kiss Cas’ open mouth, but in a heartbeat, Dean’s hand grabbed him by the upper arm and dragged him away from the temptation. Cas whined in frustration, but Dean shook his head, still between his— _his_ —boyfriend’s legs. Sam caught the movement and understood. While he had been invited to play, there were limits, and kissing Cas was clearly beyond those limits.

Dean pulled his mouth away and smirked up at his baby brother. “I think he can take more now,” he said, shifting up to his knees. Sam moved to add a second finger, but Dean stopped him yet again. Before Sam could bitch about the ridiculous constraints, Dean slid his own index finger into Cas, right along Sam’s own. “How’s that, Cas?”

“ _Fuck_ ,” Cas moaned. His arms flopped wide and open on the mattress.

“Yeah,” Dean agreed, pumping his finger with the same rhythm as his brother. Sam turned his head to Dean, his eyes glazed over with something akin to awe. Together. They were finger fucking Cas  _together_ , and it was awesome. “Come on, Sam, another.”

It was too soon, perhaps, but Cas didn’t object when Sam worked his middle finger in. Dean’s finger slid between Sam’s two, creating a wonderful combination of thin and stocky. Cas rocked down, fucking himself onto the amazing sensation.

“Dean,” Sam breathed, although he wasn’t sure why. But his brother was gone, bent forward to kiss Cas in a way that was forbidden to him. He kept the rhythm of his fingers as he enjoyed the pornographic exchange of tongues and breaths. He waited for Dean to give him permission to do more. There was no doubt that Dean was the ringmaster.

“Come here,” Dean ordered, bringing Sam lurching forward, leaning heavily on Cas’ chest, ready to be directed. Without preamble, Dean turned his mouth to Sam’s, pushing his tongue in and showing Sam what it meant to be thoroughly kissed.

Sam kissed back and strained to keep his fingers moving steadily. Their faces brushed against Cas’ mouth, and suddenly, Cas’ tongue was there, licking at the sides of their mouths, searching for entry. Dean moved off Sam’s mouth enough to give Cas the space he needed to push his tongue against Dean’s. Sam shuddered and before he could stop it, came with his dick still tucked in his boxer shorts. He jerked away from the crowded kiss and fell on his back beside Cas, his fingers leaving Cas, panting hard and praying his eyesight returned soon.

Dean shifted again, shoving his own boxers down his thighs, and swiftly replacing the finger inside Cas with his leaking cock. Cas grabbed the headboard again and cried out as Dean thrust into him at a bruising pace. Sam rolled his head to watch. Dean let his lover beg and beg, until he took pity and wrapped a sure hand around Cas’ swollen and bouncing dick. Before the tenth rotation of his wrist, Cas shouted in Enochian and shot streams of come over his chest and stomach. Sam made a choked sound and reached his hand out to catch some of the whiteness.

With a possessive growl, Dean snatched Sam’s wrist and roughly pulled his brother’s come-covered hand to his mouth. He licked and slurped, reclaiming every drop of Cas from his greedy little brother. The taste, the smell, the feel of Cas… he came with a force that surprised them all, and with a hard bite of warning to the side of Sam’s hand.

Dean fell forward and rolled, pulling his boyfriend with him, maintaining the connection of their bodies. Cas belonged to him and now that it was done, he did not want Sam to touch what was his. Sam seemed to understand and without a word, slipped from the bed and headed to the bathroom, where he shut the door with a muted click.

“Thank you,” Cas whispered, tucking his head in the familiar dip between Dean’s shoulder and neck. “You would do anything for me.”

It wasn’t a question. It was a fact.

 


End file.
